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MoveDetectDir

Reads which way things move in a camera or any image with optical flow and turns it into left/right and down/up channels, with thresholds, inversion and filtering, for swipe and gesture triggers.

∿ CHOPs & sensing ◆ Patreon:Base

This tool unlocks with Patreon. It installs through the same picker as everything else and unlocks with the Patreon Base tier or higher, connected from inside TouchDesigner. Everything else in the toolkit stays free and MIT, and the membership is what keeps that work moving.

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What it is

MoveDetectDir watches an image and tells you which way it is moving. It runs optical flow on the input, measures how much of the flow points left, right, down and up, and when the movement passes a threshold it comes out as two channels: one for left and right, one for down and up. Wave a hand across a camera and the channel swings to the side you swiped to.

Use it to page through a slideshow with a gesture, to steer a scene from a crowd, or to trigger anything that should react to the direction of motion as well as its amount.

It is a member of the FNS operator family: pick it from the FNS tab of the OP Create dialog and it lands as one node.

Inputs and output

  • in1 (TOP): the image to watch, usually a camera.
  • out1 (CHOP): two channels, LR for left and right movement and DU for down and up.

Parameters

Custom

ControlType / defaultWhat it does
Input Filter SizeSize number7 Blur applied to the input before the optical flow, in pixels. More blur ignores small noise.
Optflow LambdaLambda number0.1 Smoothing of the optical flow: higher values give a steadier, less detailed flow.
OptFlow ThresholdThreshold number0 The smallest flow that counts as movement; weaker flow is ignored.
Move Threshold XMovethresholdx number300 How much horizontal movement it takes before LR swings left or right.
Move Threshold YMovethresholdy number300 How much vertical movement it takes before DU swings down or up.
Inverse XInversex on / offoff Flip the left/right direction, for a mirrored camera.
Inverse YInversey on / offoff Flip the down/up direction.
Filter WidthWidth number0.2 How long the output channels are smoothed over, in seconds.

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